Since its introduction in 1876, telephony communication is an integral part of modern society which allows us to communicate by voice with colleagues and family members across the country or across the world. With mobile devices, we take the ability for voice and messaging communication everywhere.
Unfortunately, one of the most frustrating aspects of modern telephony communication is spam, namely robocalls, voicemail spam and SMS spam. Despite US laws that prohibit caller ID spoofing and telephone spamming (with some exceptions), complaints on illegal calls makes record numbers year after year. The total number of complaints on illegal calls in the United States totaled more than 22 million in 2014, with about 200,000 complaints each month about robocalls alone.
While spam itself is frustrating and wastes the user's time, there is a malicious side to spam: malicious actors disseminate telephone spam with caller ID spoofing to perpetuate scams. According to a survey conducted by TrueCaller in 2014, approximately 17.6 million Americans were victims of a phone scam and lost an average of $488 per person, costing approximately $8.6 billion annually.
The rise of telephony spam is troubling, particularly when it seems that both research and community have made great strides in combating email spam. A previous survey of the telephone spam ecosystem revealed that one key difference between email and telephone communication is that the caller ID mechanism in telephone communication is not trusted and can be easily spoofed. Email has a sender IP address, and many email spam solutions take advantage of this IP address, however, the caller ID of telephone communication is trivially spoofed (in fact, there are many online services that allow one to place voice calls while changing the caller ID). Therefore, caller ID spoofing perpetuates and enables spam and scams.
In the current public switched telephone network (PSTN) caller ID scheme, the caller ID is easily spoofed, due to lack of an authentication mechanism. When the phone is ringing, it is also impossible for the user to know if the caller ID has been spoofed. The only possible way for the recipient to determine if the caller ID is legitimate is to call the caller ID number. Of course, this solution is not feasible, because it adds inconvenience, increases time delay, does not work with shared or extension lines, and adds significant cost burden on the call recipient (especially for premium or international numbers).
Corresponding reference characters indicate corresponding elements among the view of the drawings. The headings used in the figures do not limit the scope of the claims.